The world recently learned that chlorofluorocarbons ( CFCs ), an ozone-damaging industrial gas banned under the 1997 Montreal Protocol, have made an unexpected comeback, with significant emissions detected in the atmosphere. The source of these banned gases has remained unclear. Now, documents and research gathered by the New York Times and independent investigators suggest that the CFCs, specifically CFC-11, may be coming from factories in China that manufacture foam for buildings and appliances. “You had a choice: Choose the cheaper foam agent that’s not so good for the environment, or the expensive one that’s better for the environment,” factory owner Zhang Wenbo told the New York Times . “Of course, we chose the cheaper foam agent. That’s how we survived.” At the time of Zhang’s interview, local authorities were conducting inspections throughout town and citing those who violated regulations. When they arrived at his factory, they assessed that it was in violation of environmental codes and ordered it shut down. “They never told us until last year that it was damaging the atmosphere ,” Zhang said. “Nobody came to check what we were using, so we thought it was O.K.” Although some provinces in China have tightened enforcement of the CFC ban, the chemical still remains available online. “When nobody is watching, they can make some, or when they get an order — an underground order — they can also produce it,” local refrigeration expert Liu Le told the New York Times . “They produce for a while until they’re discovered, and then move on.” Related: Antarctic ozone layer shows “first fingerprints of healing” The U.S.-based Environmental Investigation Agency has determined that at least eight factories in four provinces are still using CFCs to create foam. “The scale of this environmental crime is devastating, with massive potential impact on the climate and the ozone layer,” executive director Alexander von Bismarck said. “We’re hoping for a strong response from a strong environmental agreement.” While the mystery is becoming more clear, there is much more that needs to be done to determine the full extent of the problem. Head of the United Nations Environment Program Erik Solheim said, “Based on the scale of detected emissions there is good reason to believe the problem extends beyond these uncovered cases.” Via New York Times Image via Depositphotos